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Regulation of ubiquitin-dependent cargo sorting by multiple endocytic adaptors at the plasma membrane.

ABSTRACT: Endocytic protein trafficking is directed by sorting signals on cargo molecules that are recognized by cytosolic adaptor proteins. However, the steps necessary to segregate the variety of cargoes during endocytosis remain poorly defined. Using Caenorhabditis elegans, we demonstrate that multiple plasma membrane endocytic adaptors function redundantly to regulate clathrin-mediated endocytosis and to recruit components of the endosomal sorting complex required for transport (ESCRT) machinery to the cell surface to direct the sorting of ubiquitin-modified substrates. Moreover, our data suggest that preassembly of cargoes with the ESCRT-0 complex at the plasma membrane enhances the efficiency of downstream sorting events in the endolysosomal system. In the absence of a heterooligomeric adaptor complex composed of FCHO, Eps15, and intersectin, ESCRT-0 accumulation at the cell surface is diminished, and the degradation of a ubiquitin-modified cargo slows significantly without affecting the rate of its clathrin-mediated internalization. Consistent with a role for the ESCRT machinery during cargo endocytosis, we further show that the ESCRT-0 complex accumulates at a subset of clathrin-coated pits on the surface of human cells. Our findings suggest a unique mechanism by which ubiquitin-modified cargoes are sequestered into the endolysosomal pathway.

SUBMITTER: Mayers JR

PROVIDER: S-EPMC3718112 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Regulation of ubiquitin-dependent cargo sorting by multiple endocytic adaptors at the plasma membrane.

Mayers Jonathan R JR Wang Lei L Pramanik Jhuma J Johnson Adam A Sarkeshik Ali A Wang Yueju Y Saengsawang Witchuda W Yates John R JR Audhya Anjon A

Proceedings of the National Academy of Sciences of the United States of America 20130701 29

Endocytic protein trafficking is directed by sorting signals on cargo molecules that are recognized by cytosolic adaptor proteins. However, the steps necessary to segregate the variety of cargoes during endocytosis remain poorly defined. Using Caenorhabditis elegans, we demonstrate that multiple plasma membrane endocytic adaptors function redundantly to regulate clathrin-mediated endocytosis and to recruit components of the endosomal sorting complex required for transport (ESCRT) machinery to th ...[more]

PMID: 23818590

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Project description:BackgroundIn yeast and mammals, many plasma membrane (PM) proteins destined for degradation are tagged with ubiquitin. These ubiquitinated proteins are internalized into clathrin-coated vesicles and are transported to early endosomal compartments. There, ubiquitinated proteins are sorted by the endosomal sorting complex required for transport (ESCRT) machinery into the intraluminal vesicles of multivesicular endosomes. Degradation of these proteins occurs after endosomes fuse with lysosomes/lytic vacuoles to release their content into the lumen. In plants, some PM proteins, which cycle between the PM and endosomal compartments, have been found to be ubiquitinated, but it is unclear whether ubiquitin is sufficient to mediate internalization and thus acts as a primary sorting signal for the endocytic pathway. To test whether plants use ubiquitin as a signal for the degradation of membrane proteins, we have translationally fused ubiquitin to different fluorescent reporters for the plasma membrane and analyzed their transport.ResultsUbiquitin-tagged PM reporters localized to endosomes and to the lumen of the lytic vacuole in tobacco mesophyll protoplasts and in tobacco epidermal cells. The internalization of these reporters was significantly reduced if clathrin-mediated endocytosis was inhibited by the coexpression of a mutant of the clathrin heavy chain, the clathrin hub. Surprisingly, a ubiquitin-tagged reporter for the Golgi was also transported into the lumen of the vacuole. Vacuolar delivery of the reporters was abolished upon inhibition of the ESCRT machinery, indicating that the vacuolar delivery of these reporters occurs via the endocytic transport route.ConclusionsUbiquitin acts as a sorting signal at different compartments in the endomembrane system to target membrane proteins into the vacuolar degradation pathway: If displayed at the PM, ubiquitin triggers internalization of PM reporters into the endocytic transport route, but it also mediates vacuolar delivery if displayed at the Golgi. In both cases, ubiquitin-tagged proteins travel via early endosomes and multivesicular bodies to the lytic vacuole. This suggests that vacuolar degradation of ubiquitinated proteins is not restricted to PM proteins but might also facilitate the turnover of membrane proteins in the early secretory pathway.

Dataset Information

Regulation of ubiquitin-dependent cargo sorting by multiple endocytic adaptors at the plasma membrane.

Publications

Regulation of ubiquitin-dependent cargo sorting by multiple endocytic adaptors at the plasma membrane.

Similar Datasets

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